1. Field of the Invention
The present invention relates to polyester compositions, more particularly to compositions and processes which are related to chain extended polyester compositions.
2. Description of the Prior Art
Polyester compositions are known as useful in a wide range of applications as engineering materials due to their favorable physical properties. However, the use of various type of polyesters is sometimes limited due to shortcomings due to their molecular weight and/or molecular weight distribution. For example, low molecular weight polyesters may not be suitable in applications wherein a higher molecular weight material due to the physical requirements of a particular fabrication process, such as in blow molding operations and the like. To overcome such a limitation it is known to the art to provide one or more a reactive compositions to one or more polyesters to so effectuate linking of the individual polyester molecules via reactive coupling such as by reactive coupling of terminal groups to form a chain extended polyester molecule having a higher molecular weight. Other reactive coupling is also known to the art such as by cross linking two or more polyester molecules, so-called "grafting reactions" wherein one or more molecules are appended at a point intermediate the end groups in a polyester molecule chain as well as where three or more polyester molecules are coupled by their terminal groups via a reactive composition.
U.S. Pat. No. 4,568,720 provides processes for producing chain extended polyesters by reacting one or more polyesters with an effective amount of one or more phosphite compounds; toxic phenolic compounds are produced in the practice of this invention.
U.S. Pat. No. 5,037,897 provides compatabillized blends of polyphenylene oxides and polyesters which are compatibillized by the use of an effective amount of a phosphoroustrislactam.
While these and other compositions and processes in the art have provided useful methods for producing and compositions comprising chain extended polyesters there remains a continuing need in the art for compositions of and techniques for producing chain extended polyesters.